We study a toy model for phantom cosmology recently introduced in the literature and consisting of two oscillators, one of which carries negative kinetic energy. The results are compared with the exact phase space picture obtained for similar dynamical systems describing, respectively, a massive canonical scalar field conformally coupled to the spacetime curvature, and a conformally coupled mas...

We compute the propagator for massless and massive scalar fields in the metric of the pp-wave. The retarded propagator for the massless field is found to stay confined to the surface formed by null geodesics. The algebraic form of the massive propagator is found to be related in a simple way to the form of the propagator in flat spacetime. [email protected] [email protected]...

We consider the thermodynamics of minimally coupled massive scalar field in 3+1 dimensional constant curvature black hole background. The brick wall model of ’t Hooft is used. When Scharzschild like coordinates are used it is found that apart from the usual radial brick wall cut-off parammeter an angular cut-off parameter is required to regularize the solution. Free energy of the scalar field i...

In this paper we work in perturbative Quantum Gravity coupled to Scalar Matter at tree level and we introduce a new effective model in analogy with the Fermi theory of weak interaction and in relation with a previous work where we have studied only the gravity and its selfinteraction. This is an extension of the I.T.B model (Intermediate-Tensor-Boson) for gravity also to gravitational interacti...

The problem of determining the radiation reaction force experienced by a scalar charge moving in flat spacetime is investigated. A consistent renormalization procedure is used, which exploits the Poincaré invariance of the theory. Radiative parts of Noether quantities carried by massive scalar field are extracted. Energy-momentum and angular momentum balance equations yield Harish-Chandra equat...

We consider the scattering of lightlike matter in the presence of a heavy scalar object (such as the Sun or a Schwarzschild black hole). By treating general relativity as an effective field theory we directly compute the nonanalytic components of the one-loop gravitational amplitude for the scattering of massless scalars or photons from an external massive scalar field. These results allow a se...

We investigate the asymptotic tail behavior of massive scalar fields in Schwarzschild background. It is shown that the oscillatory tail of the scalar field has the decay rate of t−5/6 at asymptotically late times, and the oscillation with the period 2π/m for the field mass m is modulated by the long-term phase shift. These behaviors are qualitatively similar to those found in nearly extreme Rei...

We investigate the effect of entanglement between two causally separated open charts in de Sitter space on the spectrum of vacuum fluctuations. We consider a free massive scalar field, and construct the reduced density matrix by tracing out the vacuum state for one of the open charts, as recently derived by Maldacena and Pimentel. We formulate the mean-square vacuum fluctuations by using the re...

Scalar radiation, represented by a massless scalar field in a Robertson-Walker metric, is taken into account. By using a weak non minimum vacuum definition, the radiation temperature as a time dependent function is obtained. When the universe evolution is nearly but non equal to t, it is possible to fit the temperature of the microwave background. A particular massive case is compared with the ...

We examine the absorption cross section of the massive scalar field for the higher-dimensional extended object. Adopting the usual quantum mechanical matching conditions between the asymptotic and near-horizon solutions we check whether or not the universal property of the absorption cross section, which is that the low-energy cross section is proportional to the surface area of horizon, is mai...